The present invention relates to a lifting apparatus operated by negative pressure, and by which articles may be gripped and lifted to be displaced and transferred to a new position. Specifically, the invention relates to a vacuum operated lifting apparatus that is designed to have durable operation also in polluted or dusty environments.
As used herein, the term xe2x80x9cvacuum operatedxe2x80x9d refers to a lifting apparatus that is operated by negative pressure, such that a pressure difference between a piston pressure side and a piston suction side causes a movement in the piston, that is utilized for lifting purposes. The word vacuum is therefore to be understood as including also other conditions than conditions, completely free of pressure.
Lifting apparatus as mentioned above are known per se in process industry and used for shifting articles between work stations or process steps, e.g. In many such industries, such as the engineering industry, graphic or chemical industries, high demands are raised in aspects of durability also in harsh operational conditions. These conditions may include oil or grease, frequently combined with dust, grindings and fibers, that may intrude between slide surfaces and ports, thus reducing the operational capacity of the lifting apparatus.
The object of the present invention is to provide a vacuum operated lifting apparatus that is designed for reliable service and durable function also in harsh operational conditions.
By the way this object will be met by the invention, there is also provided a vacuum operated lifting apparatus having great versatility in implementation, and by which installation is facilitated.
In the present invention there is suggested a lifting apparatus comprising a cylinder, wherein a moving piston has a pressure side and a suction side. A piston shaft runs through a bottom of the cylinder and has a passage that connects the piston pressure side to the atmosphere. In accordance with the invention, the piston suction side defines a chamber that is connected to a vacuum source. Said chamber is designed to be evacuated from air and is axially compressible. In radial directions, the chamber is defined between the walls of flexible bellows, that are arranged concentrically about the piston shaft.